Removing overlapping objects, made with particles
go to emit from tab in particle system settings (you have to have the advanced checked), there you should have selected faces by default (if you didn't change it), then select one in particles/face.
Before:

After:

Faces:


If this doesn't work for you (you have too small faces or something) you can convert the particle system (mdifiers - particle system - convert) and then delete the overlapping bricks.